LECTURE XVI.] HISTORY OF CHEMISTRY. 351 



out encountering any contradictions in doing so, especially 

 when we take into consideration the recent experiments of 

 Walden," in accordance with which it is possible, by means of 

 simple chemical reactions, to pass at ordinary temperatures 

 from an active substance to its enantiomorph. 



As regards the application of the theory of asymmetric 

 carbon atoms to molecules with doubly linked carbon atoms, 

 a matter that van 't Hoff had already mentioned, but one which 

 had met with less attention, very special notice was called to 

 it by Wislicenus, 100 who, moreover, had himself given the first 

 impulse to stereo-chemical conceptions by his earlier and 

 extended investigations of lactic acid. 101 



The researches of Wislicenus and his pupils 102 have 

 certainly supplied most valuable contributions towards the 

 clearing up of these remarkable cases of isomerism an end 

 towards which (after the discovery of fumaric 103 and maleic 104 

 acids) a great many chemists, and even Kekule himself, 105 had 

 aspired in vain. In this domain, however, there are still many 

 unexplained contradictions, as Michael 10(5 and Anschiitz 107 in 

 particular have shown. On the other hand it must be admitted, 

 that by van 't Hoff's theory an extremely plausible explanation 

 of the products arising from the oxidation of fumaric and of 

 maleic acids is rendered possible. 108 



The applications of the doctrine of asymmetric carbon 

 atoms to substances containing rings are also important and 

 interesting. The first principles were laid down by van 't Hoff; 

 but their significance was only fully recognised when Baeyer 

 published his extended investigations upon hydrogenised 



99 Berichte. 28, 2766; 29, 133; 30, 2795 and 3 146. 10 Uber die raumliche 

 Anordnung der Atome in organischen Molekulen und ihre Bestimmung 

 in geometrisch - isomeren ungesattigten Verbindungen, Leipzig 1887. 

 101 Annalen. 125, 41 ; 128, I ; 133, 257 ; 146, 145 ; 166, 3 ; and especially 

 167, 345- 102 Ibid. 246, 53 ; 248, i, 281 ; 250, 224 ; 272, i ; 274, 99. 

 10:5 Pfaff, in Berzelius' Jahresbericht. 1828, 216. 104 Pelouze, Annalen. 

 II, 263. 105 Annalen. Supplementband 2, in ; Zeitschrift fiir Chemie. 

 10, 654. 106 J. pr. Chem. [2] 38 ; 43 ; 46 ; 52; etc. lo7 Annalen. 

 254, 168. 108 Kekule and Anschiitz, Berichte. 13, 2150 ; 14, 713. 



